Heretofore, no storage cathode-ray-tube having therein a single on axis writing gun to provide the principle electron beam and a single off-axis flood gun to provide the flood electron beam so as to write and store an image on the fluorescent screen of the cathode-ray-tube has been provided because of non-symmetrical geometry in optical representations caused by electron-electron interaction of the flood and writing electron beams under the control of electrical signals during storage operation.
Distortions, as described above, to the image produced on the fluorescent screen due to electron-electron interaction are well known. For example, in single gun cathode-ray-tubes using electrostatic deflecting devices, one cause of such distortions are the effects of a non-uniform electric field between one of the pairs of deflecting plates.
To eliminate the distortions in single gun cathode-ray-tubes conventional arrangements including magnet poles arranged adjacent the point of impact of the electron beam remote from the point of deflection have been used.
In storage cathode-ray-tubes, the distortions are eliminated by providing within such tubes two flood guns and operated in a conventional manner. Another conventional means to eliminate such distortions which is applicable to both single gun cathode-ray-tubes and storage cathode-ray tubes having a plurality of electron guns is by varying the voltage on a wallband electrode coated on the inner surface of the tube envelope and positioned between the output ends of the deflection means and the fluorescent screen.
However, the above described means to correct the non-symmetrical geometry in optical representations are not effective when using a on axis single writing gun and a single off-axis flood gun due to the fact that compensation occurs at all times, hence, would cause further distortions. For example, if the magnet pole correction means were used as disclosed in U.S. Pat. No. 2,258,643 and were applicable to storage cathode-ray-tubes, it would be necessary to remove such magnets during storage operation to prevent interaction of the field produced by such magnet poles and the flood electron beam during storage operation. To remove these means during storage operation would be impractical, if not impossible.